A ball valve is a common type of mechanism for controlling the flow of a fluid through a pipeline. Such a valve has a housing with an inlet opening and an outlet opening to which sections of the pipeline are attached. Within the housing is a ball that has an aperture therethrough. The ball is attached to one end of a stem which extends through din opening in the housing and has a lever handle attached to the exterior end of the stem. The user is able to rotate the lever handle causing a corresponding rotation of the ball inside the valve housing. In a first orientation of the ball, the aperture therethrough is aligned with the inlet and outlet openings allowing the fluid to flow through the valve. When the handle is rotated ninety degrees from the first orientation, the aperture through the ball no longer is aligned with the inlet and outlet openings, instead a solid portion of the ball blocks fluid flow through the valve. The lever handle and the attached ball can be placed at other positions between the fully opened and fully closed orientations to throttle the flow of fluid through the valve.
In many applications of a ball valve, it is desirable to prevent unauthorized operation. Therefore, a locking mechanism is required to preclude moving the valve lever handle from either the fully opened or fully closed position without appropriate authorization. For example, when maintenance is being performed on equipment downstream from the valve, it is often necessary to lock the valve in a closed state to prevent someone from inadvertently opening the valve,, thereby releasing hazardous energy resulting in harm to personnel or equipment. There may also be a need to lock the valve in a specific throttle position to prevent someone from either increasing or decreasing the flow of fluid.
Further, there is a need for a device of the foregoing type that can be retrofitted to existing valves so as to obviate the expense of replacing many valves now in service with new valves that include a built-in locking feature. Lever handle operated ball valves also come in a wide variety of sizes and it is advantageous to enable a single locking mechanism to be utilized on a variety of different sizes and shapes of ball valves/block valves.